1. Field of the Invention
The present invention relates to external ventricular drain systems and, more particularly, to a wearable external ventricular drain system.
2. Description of the Related Art
Hydrocephalus is a medical condition characterized by an excess accumulation of fluid in the brain. It results in increased intracranial pressure (“ICP”) and can cause severe brain damage or death if the pressure is not relieved. An external ventricular drain (“EVD”) is used to drain excess cerebrospinal fluid (“CSF”) in cases of temporary hydrocephalus such as brain hemorrhage and shunt malfunction in order to provide a therapeutic reduction in ICP.
The currently existing EVD system consists of a thin soft tube (ventricular catheter) that is inserted under sterile procedure into the ventricle of the brain. The distal end of the ventricular catheter is connected to the EVD tubing which leads to a drip chamber with an adjustable height that is mounted to a frame. This tubing is rigid in order to prevent damping of pressure pulsation coming from the brain. On the frame of the EVD are pressure markings and the system is leveled to the patient's ventricle at the level of zero pressure by adjusting the system height vertically to set the zero level of the system level with the patient's ventricles.
The drip chamber has volume markings to allow for recording of the amount of fluid collected per time increment (typically hourly) and is emptied into a larger bag using a three-way stopcock after the output has been recorded. The tubing between the ventricle and the drip chamber generally includes a port that can be used for sampling CSF. A three-way stopcock connects the tubing to the drip chamber so the drain can be closed off from draining entirely, or allow for pressure measurement without draining fluid.
A pressure transducer may be connected to the system before the drip chamber at the level of the patient's ventricle (zero pressure mark on the EVD) to measure the pressure in the brain when the drain is closed. The entire EVD system is mounted on an intravenous drip (“IV”) pole where the EVD system can be raised and lowered as needed to maintain level with the ventricle. The pressure transducer is kept at a position that is level with the patient's ventricle and is connected to one branch of a three way stopcock. The reason for this connection is that the true pressure in the brain can only be measured when CSF flow is stopped (valve closed to drainage). The rigid tubing between the patient's brain and the pressure transducer does not affect the pressure reading, as it is an extension of the rigid cranial compartment. The transducer connects wirelessly or via cable to a monitor. The monitor generally displays an average ICP along with a pressure waveform. In the ICU setting, the nurse on call must be able to view an ICP waveform while draining CSF (valve open to pressure transducer, and to flow), or while the drain is closed.
The greatest issue with the current EVD system is that the zero level of the drain must be level with the patient's ventricle at all times. If the drain is not level with the patient's ventricle, more or less back pressure will be applied to the brain, and thus more or less CSF than desired will flow into the drip chamber. This requirement causes decreased safety to the patient and increased nursing time necessary to level the drain, as patients are prone to frequently adjusting the positions and elevations of their heads.
For example, many ICU patients with hydrocephalus have neurological deficits and cannot always remember that they have an EVD. These patients are likely to sit up quickly, which results in over-drainage of CSF into the EVD. Over-drainage can be very hazardous to the patient, possibly causing increased headache, collapse of ventricles, decreased cerebral perfusion, hemorrhage, and death. In addition, if the patient adjusts his/her bed from an elevated position to a horizontal position, under-drainage of CSF would occur. Under-drainage of CSF can lead to a dangerous over-accumulation of fluid in the brain, possibly causing headaches, nausea, brain damage, brain herniation, and death.
Conventional EVD systems thus result in decreased mobility and independence for ICU patients, which lead to poorer outcomes and loss of function while the patients are hospitalized. Brain bleeds and shunt infections may require the patient to be tethered to an EVD for a period of weeks. Each EVD patient must be closely visually monitored so that that the nurse can intervene as soon as the patient moves. Mobile ICU patients must ring their call bells each time they want to move so that the nurses can close and readjust the height of their EVD systems in order to maintain the zero levels of their EVDs relative to the patients' ventricles. Only properly trained nurses can adjust the EVD drain, so this requirement prevents other health care workers or family members from being able to assist the patients to reposition their heads, or move about the room or hospital.
Additionally, as a patient recovers, the patient's treatment may include physical therapy, which requires the patient to leave the bed. The patient or nurse then must bring the EVD, which is attached to an IV pole, and its lengthy tubing along with the patient. This procedure adds the risk of the patient tripping, and limits the amount of time that the patient can be out of the bed, since the EVD must be adjusted or turned off and closely monitored in order for the patient to stand.